I never did that. Though I would love to learn how to do it (and guess it musn't be too difficult since they would be losing money).
Anyway, we have another problem there, if you want to export to iOS you need to have a Mac and also an iPhone if its going for mobile. I don't own any of those. Know people who does, so maybe I can borrow those or, if you have, you can export the builds. I would do first the Android version to make sure everything works and then Unity let's you export (with a mac license) the same project for iOS.
I know I am not selling myself as the best partner ever haha but I want to be totally honest.
MonoFlauta
I don't consider myself an expert in unity, neither english, and I never finished a Unity mobile game. But I am the programmer of Witchcraft https://witchcraft.itch.io/witchcraft (we are still working on it) that is made in Unity. If you think it's good enough and want, I would gladly see what needs to be done :)
BoMToons
Do you have any experience setting up In-App-Purchases for mobile on iOS and Android? If not, how daunting does that sound to you?